1. Field of the Invention
The present invention relates to a substrate processing apparatus and a substrate processing method which process a substrate. Examples of the substrate to be processed include semiconductor wafers, substrates for liquid crystal display devices, substrates for plasma display devices, substrates for FED (Field Emission Display) devices, substrates for optical disks, substrates for magnetic disks, substrates for magneto-optical disks and substrates for photo masks.
2. Description of Related Art
In a manufacturing process for a semiconductor device or a liquid crystal display, etc., a cleaning process of removing particles and other foreign matter from a substrate, such as a semiconductor wafer or a liquid crystal display glass substrate, etc., is performed. The cleaning process is performed, for example, by spray cleaning, in which a large number of liquid droplets are collided against the substrate, or by ultrasonic cleaning, in which ultrasonic waves are applied to a processing liquid on a substrate. U.S. Patent Application Publication No. 2006/266382 A1 discloses a cleaning method in which an aqueous film covering a front surface of a substrate is expanded by freezing and adhesion of particles with respect to the substrate is weakened thereby.
In a cleaning process, it is required that particles be removed from the substrate while preventing collapsing of patterns formed on the substrate. However, as patterns are being made finer and finer, the patterns are lowered in strength and therefore with the spray cleaning and ultrasonic cleaning, the patterns may collapse. Although a method with which momenta of the liquid droplets collided against the substrate or the ultrasonic waves are weakened may be considered, an adequate cleaning effect cannot be obtained with this method. Also with the cleaning method according to U.S. Patent Application Publication No. 2006/266382 A1, a processing time is increased because the aqueous film covering the front surface of the substrate must be frozen and the frozen aqueous film must be thawed and removed from the substrate.